


3/4 of the Way

by orphan_account



Series: A Natural Response [1]
Category: Big Hero 6 (2014)
Genre: Anal Fingering, Canon Character of Color, First Time Blow Jobs, Fluff, M/M, Prostate Milking, Queer Character, Sex Toys, Sexual Experimentation, Shameless Smut, Sibling Incest, Smut, Vibrators, Voyeurism
Language: English
Status: Completed
Published: 2014-11-24
Updated: 2014-11-24
Packaged: 2018-02-26 22:02:56
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 4,259
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2667983
Author URL: https://archiveofourown.org/users/orphan_account/pseuds/orphan_account
Summary: <blockquote class="userstuff">
              <p>It isn't necessarily common, he knows, for a child to be so … aware from such a young age. Certainly his sexual awakening would have been less embarrassing had it also not been for the glaring fact that despite his mental maturity, his body still had (has) yet to catch up. As Hiro is painfully aware, it becomes difficult to experiment when the only other sexually active persons happen to be at least ten years older, and acquiring and keeping any special devices must be snuck beneath the nose of one particularly overprotective older brother.</p><p>Needless to say, such a rare occasion as tonight—nearly midnight on a Wednesday—is one Hiro plans to take full advantage of.</p>
            </blockquote>





	3/4 of the Way

**Author's Note:**

> *sweats nervously*

What Hiro lacks in physical maturity, he finds he more than makes up for in mental capacity. He's known this for years—made enough casual observation to notice all the striking disparities. Though his extreme intelligence often dwarfed those who were his age, even the shortest children born in the same year still towered almost a foot over him and were nowhere near as gangly. By the time he'd become partially fluent in Japanese, Mandarin Chinese, and Latin, the few friends he'd managed to procure that were his age were growing large quantities of body hair and acquiring new curves. The twenty minutes it took him to come up with the idea for his battle-bot was also the same time it took him to run ¾ of a mile.

And none of this would be a problem.

Except by the time his fellow eleven-year-olds were being given the "birds and the bees" talk, he was already fully aware of "where everything went", what his romantic and sexual orientations were (panromantic and fluid), and had a surprisingly applicable knowledge of oral, anal, and vaginal intercourse.

It isn't necessarily common, he knows, for a child to be so … aware from such a young age. Certainly his sexual awakening would have been less embarrassing had it also not been for the glaring fact that despite his mental maturity, his body still had (has) yet to catch up. As Hiro is painfully aware, it becomes difficult to experiment when the only other sexually active persons happen to be at least ten years older, and acquiring and keeping any _special_ devices must be snuck beneath the nose of one particularly overprotective older brother.

Needless to say, such a rare occasion as tonight—nearly midnight on a Wednesday—is one Hiro plans to take full advantage of.

It's been getting worse lately, Hiro notes. At fifteen with his hormones running quite rampant, he's found it particularly inconvenient to attempt dealing with his constant and (mostly) irregular bodily functions and reactions. Hiro is certain that other young adults, while they may experience similar hormone levels, do not also have annoying older brothers and college-age friends who understand neither the concept of knocking nor of privacy.

(Hiro is fairly sure Wasabi will never look at him the same way again.)

But this time is different.

 _No one's going to come up here,_ Hiro tries to tell himself as he cast wary glances towards the door. After all, it's close to midnight, and on a Wednesday, no less. Aunt Cass is probably in bed by now, exhausted from the day's work in the café and likely dead to the world. She wouldn't wake up even if Hiro shouted in her ear. (He's tried before, when he was little.) Baymax is at the university, neatly tucked in a box in the nerd lab. And when he'd left the university for the day, Tadashi was likely still at the university lab, working on his next big project. Hiro is sure that, on the off chance that Tadashi does return, it will be after sunrise, probably collapsing in his bed and sleeping until he has to return to class a few hours later.

Biting his lips nervously, he scoots to the edge of his bed and scrambles across the floor, skidding to a halt in front of his computer and scurrying beneath the desk. He digs through the messy scraps of old essays and lab reports, wrinkled lined paper, and science projects he'd neglected to throw away, pulling out a small box with shaky fingers.

He almost laughs at himself for how jittery he is, but any chance of nervous laughter dies away in his throat as he flips open the lid and lifts out a thin silicone vibrator, black and curved slightly. He touches its tip, flicking the on switch on its handle, and shivers as it comes to life.

Hiro turns it off. "Battery powered for easy operation," Hiro mumbles, replacing the papers and parts as neatly as he can before slipping back to the bed. He sets the vibrator and its box down, fumbling with a small bottle of water-based lube and trying to warm it with one hand while he tugs his shirt and hoodie off, unbuttoning and unzipping his pants slowly.

He's done this before, when he first got the product in the mail several weeks ago. While he didn't get to finish and he knew his reach wasn't quite long enough to push the vibrator in all the way and maintain perfect control of it, he'd caught on quickly enough.

With a small whimper, he leans forward to rest his face against his pillow, stroking himself slowly with a hand and squeaking softly as he rubs a thumb over the slit at the tip. He traces one lubed finger down his spine and down his crease, jolting slightly as he strokes over the fluttering pucker of his hole.

He releases a long breath to relax a bit, and slides the finger in gently, thankful he'd taken the time to prepare himself a bit earlier in the shower. He's loose enough to comfortably fit two fingers, but he takes time to make sure he can handle the vibrator, thrusting them back and forth and shuddering.

"Nnghh—" He gasps into the pillow as he just grazes his prostate, clenching around his fingers and fisting the sheets. He slips another finger in, biting back a moan. He flushes at how _dirty_ this feels: the slick sound of him fucking himself on his fingers, blood heat flushing his skin hot and thundering around him, rapid-staccato heartbeat thumping in his ears.

Hiro had planned to wait another five minutes at least, just in case, but two minutes later he's too hard to care. He reaches down to grasp the vibrator, resting the head against his madly twitching hole and whining as he slips just its head in. He pauses for a moment, trembling, and then slides it in further with a gasp.

It feels just like remembered—he's loose and richly slippery, and so the thick head presses in deep, the taper stretching him beautifully. His breaths come out in sharp, shallow puffs as he slides it in, unable to keep wet cries from bursting from his mouth as he pushes it in as far as he safely can. He rests for a moment, trembling, and then pulls it back out, thrusting it back in.

"Mmhn—ah, ahh, _ahhngh—"_

He loses himself for what feels like forever, unable to focus on anything but the sensation of silicone tugging on his rim and rubbing inside him, barely able to contain the increasingly animal noises rumbling from his chest and bubbling up out of his throat.

Eventually, he remembers exactly why he bought a _vibrator_ instead of a dildo, and with a shaky gasp, clenching wetly around the slippery black phallus, he flicks it on to its lowest setting.

Hiro's scream is only just muffled by the pillow he's buried his face in.

* * *

It's almost one o'clock by the time Tadashi putters into the garage on his scooter, tugging off his helmet and stumbling off the back of it. He's exhausted, sure, but certainly proud; he doesn't usually come home this early, and he's sure he'll get lots of sleep tonight, able to wake up early enough to be the one to drag his brother out of bed and nudge him along to class before he heads to the lab again while still getting a decent amount of sleep.

Okay, so he would've stayed later, but he'd gotten so involved in his new project that it was eleven before he took a break and realized that practically everyone else in the lab, including Hiro, had already gone home without him and that he hadn't eaten dinner.

The moment he enters the café, his mouth begins to water. He knew it. Aunt Cass had made her wings. His stomach grumbles, and he hurries to the kitchen, tiptoeing up the staircase with a hopeful hum. If he's lucky, Hiro didn't eat all the wings like he usually tries to.

"No guarantees," Tadashi mutters under his breath, and makes his way to the fridge, gracefully snatching a glass and the carton of mango and litchi juice from the fridge.

He lets out a quiet cheer when he sees the Tupperware with the wings and the sauce, setting them down on the kitchen counter. He decides to eat them cold—the microwave is too noisy to cook them, anyway—and pours himself a glass, taking a long gulp, walking idly around the kitchen.

He frowns as he nears the stairs, hearing a whimper, and sets the glass down on the kitchen table. Another muffled noise, then a whine. Above it all, there is a soft, wet squelching noise; it's somehow familiar, but something he can't quite place.

"Did Mochi get stuck between the toilet and the bath again?" Tadashi mutters, moving quietly up the staircase. As he nears the room he shares with his little brother, the noise gets louder—the door is shut tight. The thin squelching noise, he realizes, accompanies a soft, stuttering whir, uneven and irregular. His eyes narrow, and he pauses at the door. Is Hiro … ?

A particularly loud, muffled cry makes Tadashi freeze, hand on the knob, and comprehension dawns over his expression, pink rushing into his cheeks and turning his ears red. Oh, gods. Oh, _gods._

His hands clench the doorknob tightly, dinner completely forgotten, and tries not to listen to the sound of his brother sobbing into his mattress, fucking himself with what sounds like a vibrator he got from god-knows-where, probably fumbling with it—he's still not grown into his body, so he's probably unable to reach—not be able to slide it in all the way—

"No, no, no, _not the time,"_ Tadashi snarls under his breath, clutching at the door frame as blood rushes south so quickly he feels dizzy.

A gasping, desperate scream interrupts his anxious fretting, and Tadashi's eyes slam shut, hand flying up to cover his mouth and stifle a groan. He's harder than he's ever been in his life, for his _brother_ of all people. His little brother, who's fifteen and still hasn't quite filled out yet, is still a bit gangly, who still looks at him with that same sort of exasperated fondness that he has since he's been little, still clings to him when he's scared, still—dear gods, he must have switched the vibrator up a level, and oh gods he's so _noisy …_

He presses a hand to his crotch, trying to relieve some of the pressure, but then Hiro moans, long and filthy, and it finally occurs to Tadashi that he may actually come from simply listening to his brother masturbate.

Or is he _masturbating?_ Tadashi thinks hazily. Hiro isn't fully grown, but he's no less beautiful for it, with his big brown eyes, kitten-soft hair, and high, round cheekbones. No, with the way Hiro laughs, the way his grin stretches across his cheeks, the way he feels snuggled up against your chest with his arms around your neck … he'd have no trouble finding a partner …

Tadashi shudders at the vicious spike of jealousy that shoots through his chest. _Someone else,_ he thinks, _touching my brother, trailing their fingers down Hiro's skin, spreading those pert little cheeks of his, lapping at his twitching hole, thrusting their tongue in and out until Hiro wails, looming above my brother … my little brother, where I should be—_

Before Tadashi can stop to think clearly, he shoves the door open with a gasp, and from the bed, Hiro startles, swears, and fumbles, diving beneath the sheets and falling completely still. Tadashi freezes where he stands, shocked and dazed and still ridiculously hard, and stares at his brother, who hides trembling underneath his comforter. The buzz from the vibrator has stopped, and Hiro is trying to stifle soft little whimpers. It's this that prompts Tadashi into speaking.

"H—Hiro?"

Hiro doesn't respond except to shift, attempting to bury himself in his bedspread. He squirms, then yelps, and Tadashi starts and hurries to tug the covers away from Hiro's face.

Hiro's eyes are bright and glistening, his lower lip trembling. He looks so delicate, Tadashi thinks, and his chest aches as he reaches out and scoops Hiro into his arms.

His little brother squeaks. "Er—Nii-chan, this … this isn't what it looks like."

"Not what it looks like."

"Uhhh … no." Hiro appears to be turning the exact shade of a ripe tomato. "It's. Um. I'm."

"You're masturbating," Tadashi says. The words feel bald.

Hiro jerks and stutters. It seems the flush is extending down his chest. Tadashi finds himself wondering if his rump is blushing as well and has to smack himself internally. "I—well, w-why didn't you knock?"

"It's my room, too." He's not quite sure how he's managing to keep his voice so steady; he's not entirely sure how well he can think with most of his blood currently residing south. He thinks vaguely that Hiro can feel how hard he is.

"Um." Hiro ducks his head, refusing to meet Tadashi's gaze. "So. You're home early."

Tadashi says nothing; Hiro is still squirming around in his lap. There is a soft squelch, and Tadashi realizes the vibrator, though off, is still rubbing inside his brother, stretching him wide, and Tadashi has to close his eyes at the image.

"Yeah," Tadashi breathes. "Earlier than usual." There is a pregnant pause, then: "Hiro, I—"

"Nii-chan, I'm sorry—"

"What? No, Ototo—"

"—probably really awkward for you—"

"—I shouldn't have been listening—"

"—we can just pretend this never happened—"

"—i-if you need help with this sort of thing—"

"You—wait, _what?"_

Tadashi stops as he realizes what he's just said and implied. Hiro's face burns, probably in humiliation, and Tadashi swallows hard. "Ah … What I mean is, if you're having … um, urges and things, and you need help … well, I mean, I'm your brother, and it's not like you can ask Aunt Cass about this sort of thing, so … " He trails off.

"I—" Hiro hesitates, and Tadashi feels his breath catch in his chest. _He's considering it._

Hiro's gaze drops, lashes fluttering, and he reaches a hand back, grasping the vibrator's handle. His lower lip trembles before he pulls it into his mouth, biting down gently on the soft flesh as he tries to pull it out. The position is awkward and he clearly can't quite reach. The tiny wince Hiro makes is what pushes Tadashi to reach his own hand around and nudge Hiro's out of the way.

It's only three-fourths of the way in.

"Tadashi?"

Hiro's eyes are wide, but something deeper, a darker emotion, bleeds at the corners of his coffee-colored irises as he clutches at Tadashi's shirt. Tadashi knows it's mirrored in his own eyes, knows what it makes them and what it means, knows what could happen if he doesn't shut this down like a good big brother should.

He lays them back, one arm still securely around Hiro's waist, nestling his little brother on the hard planes of his stomach before he tugs Hiro down and captures his mouth in a kiss.

* * *

He's on his hands and knees, back arched, arse in the air with his cheeks spread wide, as if on display. Tadashi is behind him, keeping him steady with strong and familiar hands and soft whispers that send sparks up his spine. His brother pulls the humming vibrator in his arse nearly out before plunging it back in to its hilt.

"Ta-Tadashi—" Hiro pleads, legs quivering, and Tadashi slows, pressing a tender kiss between his younger brother's shoulder blades.

"All right?" Tadashi asks gently, and Hiro makes a desperate sound in the back of his throat, hands scrabbling at the sheets as his brother angles the vibrator gently, strokes along his inner walls until he finds what he's looking for. He keeps the head of it pressed there, right up against his prostate, and flicks it up another setting.

Hiro gives a startled, shuddering cry, limbs trembling violently. "Hah—ahhnn—" His arms give way, as his brother begins to thrust the phallus in and out, hands scrabbling uselessly against the sheets with only his legs propping him up. "Ta—" he gasps, voice garbled and needy. A pool of precum blooms on the sheets beneath him.

Tadashi stills, and Hiro growls in frustration. "Do you need me to stop?" he murmurs, nosing softly against Hiro's shoulder. "It's okay if it's too much for you to—"

Hiro cuts him off with an angry whine, grinding back against the device and lifting his head just high enough to glower at him. Tadashi chuckles softly and switches it to its highest setting, humming as Hiro's breath catches in his throat, eyes shooting wide open. He lowers his head to lap at the sweat beading at the small of Hiro's back and drives the toy in deep, in and out as far as he can go, enjoying the way every thrust forces a cry from Hiro's lips. He steadies his brother with a hand on his hip as Hiro writhes and fights for breath, hole spasming around black silicone.

"It's okay," Tadashi breathes against his skin, leaning forward to nuzzle his brother's neck and press kisses into his hair. Hiro jolts at the change in angle, arching into the touch with a whine. "It's okay, I've got you."

"Nii-chan, _please,"_ Hiro begs; he tries to prop himself up on his elbows, only managing to hold himself up for a fraction of a second before he collapses again with a whimper. Tadashi holds back a grin and leans forward to nip at the fluttering pulse on Hiro's neck. He rubs the buzzing head of the toy in tiny, intent, merciless circles against Hiro's prostate and reaches around to stroke his brother's cock.

"Nnnh— _ahhh—Ta—da … "_

A half-cry, half sob bursts from Hiro's throat, and he jerks as he comes, white striping the sheets beneath him. Tadashi doesn't stop, simply lowers the settings and draws him through his climax and the aftershocks until Hiro bats weakly at him, muttering and sighing. Tadashi scoops him into his arms and rests him against his slightly sweaty, naked chest with ease, crooning in his ear.

"You did so good," Tadashi whispers, brushing his lips softly against his brother's temple. The boy grumbles, limp in his brother's arms, and weakly flops one hand up to brush at Tadashi's head when he buries his face in Hiro's neck and strokes his little brother's hair.

"Nii-chan, that's not fair," Hiro mumbles, chest rising and falling heavily. "You … can't just flop me around like a rag doll."

"But you're a very sexy rag doll," Tadashi teases, then laughs when Hiro glances up at him with one brow raised, unimpressed. "Anyways, Ototo, I need to clean you. You're very dirty."

Hiro's half-lidded eyes darken, and he reaches down between their legs, wrapping his fingers around his brother. Tadashi shudders, arching into the touch as Hiro begins to stroke him. "And you're very hard."

Tadashi flips Hiro around to face him, cupping his little brother's face in his hands and bringing their lips together with a breathy moan. Hiro hums happily, resuming his incessant rhythm. He nudges Tadashi's hands away to slither down to crotch level and slides down Tadashi's boxer briefs, fixing his gaze intently on his brother's cock.

 _It's a very nice cock,_ Hiro thinks. With the foreskin down, it's the same soft pink skin as Tadashi's lips, the head a bit reddish and plump. It's not a wide girth, but it's long and curves up just a bit, a thin vein pulsing high up on the underside of the shaft. _A nice cock for fucking, I bet._

"You sure about this?" Tadashi asks, voice strained as Hiro laps delicately at the head. "I keep telling you, you have to let me know if— _ah_ —you're not comfortable— _Gods."_ He cuts off with a shaky cry when Hiro suckles his way down the shaft. "Hiro, you little—"

Hiro smiled crookedly. "Unless _you_ want to back out." And then he takes the tip into his mouth and sucks.

Tadashi's head slams back, and he forces himself not to thrust up into Hiro's mouth, fisting his hands in the sheets and breathing hard. Hiro rumbles in delight, snickering as the vibrations make Tadashi grit his teeth, and pulls off with a pop before carefully, cautiously seeing how far he can swallow him down.

He goes to far too quickly and has to pull off when he chokes, coughing. Tadashi makes an unsettled noise and reaches out to pull Hiro to him, but Hiro swats his hand away and dives back in again, this time taking it a bit slower. He manages to swallow his brother's cock down about halfway, forcing himself not to gag, before he knows he can't go any further, and takes the rest in his hand.

A nice rhythm has always felt good when he's stroked himself, Hiro thinks, and begins bobbing his head, unconsciously hollowing his cheeks every time he pulls up. His teeth keep brushing lightly against the shaft, he isn't moving his hand enough, and his rhythm is irregular, but Tadashi seems to focus more on the way Hiro's lips are stretched around his cock, one hand stroking his wild tufts of hair. Hiro meets his gaze, dark and hungry, and shivers slightly, suckling at the head. Beads of precum taint his tongue, sharp and salty.

Hiro only gets the barest warning of his brother's hands tightening in his hair before viscous, bitter fluid hits his tongue, hot and brackish. He chokes but refuses to pull off even when Tadashi relaxes slightly, humming with displeasure.

"I should've pulled you off," Tadashi whispers, and Hiro crawls up his chest, opening his mouth. "Urgh, okay, lemme just grab you a tissue and you can—"

Hiro purrs, tugging Tadashi's face back and forcing him to watch as he swallows slowly. Tadashi's eyes go wide as he watches his little brother's throat bob, and Hiro giggles. "Too late," he breathes.

Tadashi mutters a curse under his breath. "Impudent little brat." His tone is exasperated, if a bit heated, but his eyes are calculating. Something sparks in them, and a slow, wicked smile spreads across his features. Hiro flushes, suddenly nervous, but before he can defuse the situation, Tadashi is tugging him up, throwing Hiro's legs over his shoulders and holding him there with two palms squeezing his arse. Hiro is reminded oddly of all the times he's ridden on Tadashi's shoulders.

"I still haven't cleaned you up," he murmurs against Hiro's groin, and Hiro squeaks. "Oh, look, you're hard again."

Hiro tries to throw an insult back at him, but then Tadashi's mouth is engulfing his prick, and _oh,_ Tadashi's a lot more experienced at this than he is. Hiro is only given a moment to pout over this before Tadashi slides his tongue into the slit, the soft pink muscle twitching back and forth as he sucks.

A sharp gasp flies from Hiro's throat, and the boy arches into the touch, eyes shooting open wide. He can feel Tadashi grin, and then the hands kneading his arse are spreading his cheeks, the stretch tugging at his hole.

Hiro whines, feeling lube dripping slowly from his entrance, and bats at Tadashi's head. "H-hey, wait—what are you—?"

Tadashi begins to hum nonsensically, eliciting a shriek from Hiro, and slides two of his fingers back to slip into his fluttering hole. He crooks his fingers, searching, and chuckles when Hiro jolts, keening and pulling at Tadashi's hair frantically.

"Ahh—Tadashi, please— _please, I can't, I can't—haahhnn~"_

Hiro comes with a sob, arching into Tadashi's mouth. Tadashi's fingers are relentless, milking every last drop of cum from his little brother's cock, refusing to stop twitching his tongue against Hiro's slit and suckling harshly until Hiro yanks hard on his hair with a desperate wail, the last of it spurting into Tadashi's waiting mouth.

* * *

"So this was nice," Hiro mumbles into his pillow, and Tadashi chuckles, wrapping his arms tighter around his little brother's waist.

"Was it?"

"Mmhm." A pause. "You should fuck me later."

Tadashi is speechless, staring at Hiro's smug little grin before burying his face in Hiro's hair with a groan. "You're a _wretch."_

"But I'm a sexy wretch."

Tadashi rolls his eyes and presses a kiss to Hiro's temple. "Point taken."

He watches with a soft smile on his lips as Hiro's breath slows to a steady crawl, waiting until a soft snore rises from the boy to slip out of bed. He wipes down the vibrator and places it and the tiny bottle of lube back in the box, setting it on Hiro's bedside counter.

Humming quietly, he cleans his little brother with a washcloth, nosing his cheek and murmuring soothingly in his ear when he twitches and screws up his face like he's about to wake up. It takes a moment for him to wash himself and throw on pyjamas, but far longer to dress Hiro without waking the boy up.

He hesitates for a moment, and then slips in beside Hiro, cradling the boy to his chest. In his sleep, Hiro snuggles closer, mumbling something about chocolate chip waffles. He smiles.

"Tomorrow," Tadashi whispers in his ear, and then drifts off himself to the scent of dry linen, dreaming of the dinner he'd never gotten to eat.

**Author's Note:**

> You can thank KudaKano and whitedandelions for their wonderful fics. Without them, I would not have been so obsessed with this fandom and this pairing and would not have felt it necessary to shove my own incestual little spiel in.


End file.
